Electrode materials derived from transition metals, in particular transition metals binary chalcogenides, such as TiS2, VOx (2≦x≦2.5), ternary oxides such as LiNiO2LiCoO2, Li1+xMn2−xO4 (0≦x≦1), et LiV3O8, are known. These materials are however often relatively toxic. With the exception of vanadium derivatives, the capacities are practically modest, i.e. on the order of 100 Ah·g−1, and their potential (about 4 V vs Li+/Lio are beyond the domain of stability of solid or liquid electrolytes. They are therefore problematic in terms of safety.
Organic compounds like conjugated polymers work through an insertion mechanism of anions taken from the electrolyte. The mass capacities resulting therefrom are consequently low and the cycling possibilities are disappointing.
Other known compounds are those of the polydisulfide type, which, even if they do not have intrinsic electronic conductivity, possess interesting redox properties and mass capacities ((≧300 Ah·g−1), particularly oxidizing coupling derivatives of 2,5-dimercaptothiadiazole. However, the resulting reduction products and intermediates are lithium salts like conjugated thiolates with a nitrogen atom. Delocalization of the charge on the polarisable anionic centers like sulfur and nitrogen, lead to a relatively important solubility in the electrolytes, as well as a reduced cycling life span.
Monoquinones are organic compounds known for their redox properties, but the potentials are of little interest (on the order of 2.2 V vs. Li+/Lio), and the neutral oxidized compounds are soluble in the electrolytes. Polymers bearing quinonic functions such as those resulting from hydroquinone and formaldehyde polycondensation, are not electrochemically active because of the reduced mobility of the charge carriers, ions and electrons, in the absence of highly polar protic solvents like water.